The molecular fate of transforming DNA bound to Streptococcus sanguis and pneumoniae is being studied. In S. sanguis, bound DNA is complexed to a protein, in which form it is single-stranded but resistant to nucleases specific for single-stranded DNA. The properties of this complex are under investigation, particularly with reference to its eventual association with the recipient chromosome. When the transforming DNA is of heterospecific origin, complex formation is identical to that with homospecific DNA; no alteration occurs to heterospecific DNA until the complex associates with the chromosome. This association proceeds more slowly than when the DNA is homospecific, and subsequent integration of heterospecific DNA is accompanied by breakdown of the latter. BIBLIOGRAPHIC REFERENCES: Biswas, G.D. and Ravin, A.W. 1976. Genetic hybridization of the leu-ilv region in Bacilli. J. Gen. Microbiol. 92: 398-404. Raina, J.L. and Ravin, A.W. 1976. Enhanced transformability with heterospecific DNA in a Streptococcus sanguis mutant impaired in RNA polymerase activity. J. Bacteriol. 127: 380-391.